Note: Descriptions are shown in the official language in which they were submitted.
CA 02317981 2001-O1-19
GRIT SURFACE CABLE PRODUCTS
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to mine roof cable bolts and, more
particularly, to coated mine roof cable bolts that are configured to be resin
grouted.
2. Brief Description of the Prior Art
A mine roof may be supported by a cable bolt positioned inside a
bore hole in a mine roof and resin grouted into place. Examples of mine roof
cable
bolts are disclosed in United States Patent Nos. 5,259,703 to Gillespie,
5,375,946
and 5,378,087 both to Locotos, and 6,074,134 to Stankus et al.
Cable bolts typically include a single or multi-strand cable segment,
a drive head positioned on a first end of the cable segment. A plurality of
mixing
devices may be positioned along a longitudinal axis of the cable segment, and
a
stiffening sleeve may be positioned adjacent the first end of the cable
segment.
These prior art mine roof cable bolts may be tensionable and include one or
more
mixing devices thereon.
During installation of a cable bolt and mine roof plate system, the
first end of a cable segment is generally positioned adjacent a mine roof
plate, with
the second end inserted into a bore hole created in the earth and rock
adjacent a
mine roof. Also inserted into the bore hole is a resin catalyst and an
adhesive. The
cable segment is rotated after insertion, causing the mixing devices to mix
the resin
catalyst and adhesive. The mixing devices also distribute the adhesive within
the
rock, in the cracks and crevices between individual strands of a multi-strand
cable
segment, and in voids between an outer surface of the cable segment and an
inner
wall of the bore hole. Once cured, the adhesive helps to anchor the cable
segment
CA 02317981 2000-09-12
to the earth and rock. Tensionable cable bolts are installed in a similar
manner,
except that an expansion assembly may also be included to further secure the
cable
bolt inside the bore hole and tension the bolt between the mine roof and the
expansion assembly.
One universal drawback of the cable bolt and mine roof plate
systems of the prior art is the trouble and expense associated with
incorporating
mixing devices, such as nut cages, buttons, or birdcages, into a cable
segment.
Another drawback is the stiffening sleeve positioned adjacent a first end of
the
cable segment. In theory, stiffening sleeves help protect the cable segment
and
prevent the cable bolt from kinking during insertion. However, stiffening
sleeves
do not prevent torsional deformation of the portion of the bolt not secured in
the
resin caused when torque is applied to the bolt drive head. When torque is
applied
during installation of the bolt to mix resin and/or engage a mechanical
anchor, a
second end of the cable segment decreases rotation as the mechanical anchor
and
resin restrain movement while the first end is unencumbered. This tends to
cause
twisting of the cable segment in the portion of the cable bolt between the
mine roof
and the resin. When installation is complete and torque from the bolt
installation
machine is removed, the twists in the non-resin grouted portion of the cable
untwist
which causes the tension applied to the bolt to be reduced. To counteract the
twisting of the lower (ungrouted) portion of the cable, a plurality of sleeves
or
"buttons" are fixed to the cable lower portion. However, these additional
components add to the cost of manufacturing a tensionable cable bolt.
Mixing devices and stiffening sleeves increase manufacturing costs,
increase the risk of producing nonconforming goods, and do not prevent
torsional
deformation. Hence, a need remains for a mine roof cable bolt which resists
torsional deformation during installation with subsequent loss of tension,
while
eliminating or minimizing the need for such extraneous mixing devices and/or
stiffening sleeves.
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CA 02317981 2001-O1-19
SUMMARY OF THE INVENTION
To obviate the deficiencies of the prior art, one embodiment of the
present invention generally includes a cable bolt having a coated cable
segment. The
cable segment generally includes a first end and a second end with a drive
head
positioned adjacent the first end of the cable segment.
In single cable segments, the coating is positioned adjacent an exterior
surface of the cable segment coating all or only a portion of the exterior
surface. In
multi-strand cable segments, the coating may completely or partially coat an
exterior
surface of each strand. Positioned adjacent an exterior surface of the coating
are
particulates forming a textured surface on the exterior of the cable bolt. A
tensioning
device may also be positioned along a longitudinal axis of the cable segment.
The
coating serves three primary functions. First, the coating strengthens the
cable segment
eliminating the need for a stiffening sleeve in some applications. Second, the
coating
retards torsional deformation of the cable segment bearing the coating when
torque is
applied to the drive head. Third, the coating further provides an attachment
medium for
the particulates. The particulates increase the overall surface area of the
cable segment
providing more bonding area for the resin and providing agitation of the resin
catalyst
and adhesive during mixing. The particulates, therefore, reduce the need for
mixing
devices, such as bulbs and birdcages, in some applications.
It is therefore an object of an aspect of the present invention to provide a
cable bolt that resists torsional deformation, does not require a stiffening
sleeve, and in
some applications, traditional mixing devices.
Further aspects of the invention are as follows:
A mine roof support device for use with a substantially one-inch
diameter mine roof bore hole comprising:
an elongated body having a first end, second end, an external surface,
and a cross-sectional diameter less than the diameter of said mine roof bore
hole;
a coating positioned on said external surface of said elongated member,
said coating forming a layer on said external surface; and
a plurality of particulates received in said coating,
wherein one or more of said plurality of particulates protrudes through
said layer of said coating, forming a textured surface suitable for mixing
resin.
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CA 02317981 2001-O1-19
A method for supporting a mine roof comprising of steps of:
drilling a bore hole in a mine roof;
inserting resin in said bore hole;
providing an elongated body having a first end, second end, an external
surface, a coating positioned on said external surface of said elongated body,
said
coating forming a layer, and at least on particulate received in said coating;
inserting said second end of said elongated body into said bore hole; and
rotating said elongated body such that said at least one particulate mixes
said resin.
A mine roof support device for use with a substantially one inch
diameter mine roof bore hole comprising:
a mufti-strand cable bolt having:
a first end, second end, an external surface, and a
cross-sectional diameter of about one inch or less;
a rigid coating positioned on each strand of said multi-
strand cable bolt and said external surface of said mufti-strand cable bolt,
said coating
forming a layer; and
a plurality of particulates received in said coating,
wherein said plurality of particulates protrudes through
said layer of said coating, forming a textured surface suitable for mixing
resin;
a drive head positioned adjacent said first end of said mufti-strand cable;
a barrel and wedge assembly positioned between said drive head and
said second end; and
a bearing plate positioned between said barrel and wedge assembly and
said second end.
These and other advantages of the present invention will be clarified in
the Detailed Description of the Preferred Embodiments and the attached figures
in
which like reference numerals represent like elements throughout.
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CA 02317981 2000-09-12
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side view of a prior art cable bolt having a mufti-strand
cable, birdcages, and a stiffening sleeve inserted into a cross-sectional view
of a
bore hole;
Fig. 2 is a side view of one embodiment of the cable bolt of the
present invention inserted into a cross-sectional view of a bore hole;
Fig. 3 is a side view of a second embodiment of the cable bolt of the
present invention inserted into a cross-sectional view of a bore hole;
Fig. 4 is a side view of a third embodiment of the cable bolt of the
present invention inserted into a cross-sectional view of a bore hole;
Fig. 5 is a side view of a fourth embodiment of the cable bolt of the
present invention inserted into a cross-sectional view of a bore hole; and
Fig. 6 is a perspective view of a horizontally sectional mufti-strand
cable segment, as shown in Fig. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The preferred embodiment of the cable bolt of the present invention
is generally shown in Fig. 2. For purposes of introduction, a prior art device
shown
in Fig. 1 will be discussed first.
Fig. 1 shows a typical prior art cable bolt C installed in a bore hole
B. The cable bolt C generally includes a mufti-strand M cable segment S,
birdcages G formed in a second end E of cable segment S, a stiffening sleeve L
positioned adjacent a first end F of the cable segment S, and a drive head H
positioned adjacent the first end F of the cable segment S. The cable bolt C
preferably is installed in a mine roof with a mine roof plate P positioned
adjacent
the drive head H and resin or adhesive A placed at the blind end of the bore
hole
B between an exterior surface ES of the cable bolt C and an interior surface
IS of
the bore hole B. Alternatively, the resin and adhesive A may fill all or
nearly all
of the bore hole B not occupied by the cable bolt C.
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CA 02317981 2001-O1-19
As shown in Fig. 2, the cable bolt 10 of the present invention
includes a cable segment 14, preferably, mufti-strand cable 16 constructed
from
steel or other suitable material installed in a borehole 12 with a bearing
plate 28.
The cable segment 14 has a drive head 26 with a conventional load bearing
barrel
and wedge assembly 52 positioned on a first end 24 of the cable segment 14 and
is
coated with a layer of a rigid or semi-rigid coating material 36, such as
plastic,
epoxy, resin, or other suitable material. A suitable assembly of drive head 26
with
barrel and wedge assembly 52 is disclosed in United States Patent No.
5,829,922 to
Calandra, Jr. et al. The entire length of cable segment 14 is preferably
coated, as
shown in Fig. 2, but partial coating is also envisioned.
As shown in detail in Fig. 6, coating material 36 preferably includes
an epoxy material and a plurality of particulates 40, such as grit, sand,
rock,
diamond dust, or other suitable material dispersed in the epoxy material
either on
the surface thereof or through the thickness of the coating material 36. The
individual particulates 40 should be large enough in diameter to give the
exterior
surface of the coating material 36 covering the cable segment 14 a textured
appearance and feel, but not large enough to significantly alter the overall
diameter
of the cable segment 14. The coating material 36 preferably is of the type
disclosed
in United States Patent No. 5,208,777 to Proctor et al.
It should be apparent to those in the art that the coating material 36
and the particulates 40 need not be two distinct substances provided the
coating
material 36 forms a textured exterior surface and, preferably, makes the cable
segment 14 more rigid.
The coating material 36 adds rigidity to the cable segment 14,
eliminating the need for a stiffening sleeve L, shown in Fig. 1, and reducing
torsional rotation in tensionable cable bolts 10' and 10", shown in Figs. 3
and 4.
The coating material 36 also provides a surface of adhesion between resin in a
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CA 02317981 2001-O1-19
bore hole 12 and the particulates 40. The particulates 40 increase the total
exterior
surface area of the cable segment 14 which increases the resin catalyst and
adhesive
30 bonding area. More importantly, the particulates 40 increase agitation of
the
resin catalyst and adhesive 30 when the cable segment 14 is rotated in the
bore hole
12 during mixing of the resin catalyst and adhesive 30. This agitation
eliminates the
need for adding birdcages or other traditional mixing devices to cable bolts
10
inserted into smaller bore holes 12, such as those approximately one inch or
smaller
in diameter.
In a second embodiment, shown generally in Figs. 3 and 4, the cable
bolts 10' and 10" include the cable segment 14 with the coating material 36
and a
mechanical anchor 44 threaded onto an externally threaded sleeve 46
surrounding
the second end 20 of the cable segment 14 (Fig. 4) as disclosed in Canadian
Patent
Application Serial No. 2,281,240 filed August 31, 1999, entitled "Tensionable
Cable Bolt". Alternatively, the mechanical anchor 44 and sleeve 46 may be
located
at a position intermediate the first end 24 and the second end 20 of the cable
bolt
10", also shown in Fig. 3.
In a third embodiment, shown in Fig. 5, the cable bolt 10"' includes
at least one sleeve or "button" 18 surrounding the cable segment 14 at a
position
intermediate the first and second ends 24, 20 of the cable segment 14.
Preferably, a
plurality of buttons 18 are included on cable bolt 10"'. The buttons 18 may
include
longitudinal flanges or wings 54 to increase the resin holding surface area
thereof.
The embodiment shown in Fig. 5 is used in larger bore holes 12, such as those
in the
range of one and three-eighths inches diameter or larger. It is believed that
in bore
holes 12 of one inch in diameter, the cable bolts do not require any
additional
mixing device beyond the coating material 36, as shown in Fig. 2.
The installation process for the cable bolts 10, 10', 10", and 10"'
generally includes the steps of partially or completely coating a cable
segment 14
with a textured surface, preferably, using a coating material 36 as described
above;
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CA 02317981 2000-09-12
drilling a bore hole 12 in a mine roof; inserting resin in the form of two-
part
catalyst and hardenable component packages into the bore hole 12; inserting a
second end 20 of the coated cable segment 14 into the bore hole 12 to rupture
the
catalyst and hardenable component packages; mixing the resin catalyst and
adhesive 30 by rotating the coated cable segment 14 via mine roof bolt
installation
equipment attached to the drive head 26; and allowing the resin 30 to cure.
For the
cable bolts 10' and 10", rotation of the bolt also causes expansion of the
mechanical
anchor 44 which engages with and grips the interior surface 34 of the wall
surrounding the bore hole 12. Torsional deformation of the cable segment is
significantly reduced and cable bolts 10' and 10" may be tensioned as
described in
the above-mentioned patents and patent applications. It has been found that
the
coating material 36 sufficiently stiffens the cable segment 14 which is below
the
resin 30 to prevent twisting of the cable segment 14 during installation and
tension
loss upon release of the bolts 10' and 10" from installation equipment.
It is believed that rotation of the cable segment 14 with the coating
material 36 sufficiently mixes resin in a one-inch bore hole 12. The
particulates
40 embedded in the epoxy material of the coating material 36 provide enhanced
mixing over uncoated cable. In addition, the increased surface area of the
cable
bolts 10, 10', 10", and 10"' of the present invention over uncoated cable
segments 14 creates higher holding strength with the resin. In pull tests,
cable
bolts according to the present invention resisted deflection when subjected to
pull
forces of between 20 and 29 tons. Hence, the present invention includes a
cable
bolt coated with a textured material without any alteration to the wrapped
strands
of the cable segment 14, such as birdcages, nutcages, or bulbs and also
includes a
method of installing the inventive cable bolt in resin containing bore holes.
For
larger diameter bore holes (e.g., one and three-eighths inches), altered cable
again
is believed to be unnecessary to achieve sufficient resin and adhesive 30
mixing
and bonding. However, in certain circumstances simple mixing devices, such as
buttons, are required as shown in Fig. 5.
CA 02317981 2000-09-12
The present invention eliminates the need for a stiffening sleeve L,
traditional mixing devices, such as birdcages, or both from conventional mine
roof
cable bolts while still retarding torsional rotation (in tensionable cable
bolts). The
textured surface of the cable segment 14 serves to mix the resin 30, provide
increased bonding area on the cable segment 14, and increase friction between
the
resin 30 and the cable bolts 10, 10', 10", and 10"'. Moreover, torsional
rotation of
cable segments 14 in tensionable cable bolts 10' and 10" is reduced within.
The invention has been described with reference to the preferred
embodiments. Obvious modifications and alterations will occur to others upon
reading and understanding the preceding detailed description. It is intended
that
the invention be construed as including all such modifications and
alterations.
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